you can either add common salt to sulfuric acid or you can form chlorine and hydrogen through electrolysis of salt water. you combust these together to make hydrogen chloride and you then bubble this through water to make hydrochloric acid

Some sink unblockers have HCl in them as I found out when one broke and went all over my hands, it is pretty dilute and would need purifying which could probably be done by make some of the other components precipitate.

As long as it didn't matter if it is rather impure that would get you some.

1. The electrolysis itself is not trivial. You will need an adjustable 0-5V DC supply to get the right bias voltage.

2. The collection of the gases will be difficult. Hydrogen is a dangerous gas...it blows the hell up if activated in the presence of air. If you have any hydrogen floating around when you throw a switch (for instance, the one on your power supply), you are essentially setting off a bomb.

3. Chlorine is heavier than air (you will have to collect it over water, but it is partially soluble in water - coincidentally, making a very weak solution of HCl)), and poisonous. You do not want to risk ihnhaling it. If some leaks out of your collection system, it doesn't float away very fast.

4. Chlorine doesn't just "react" with hydrogen, it explodes. Like many other photochemical chain reactions, it is very tricky to control the rate of reaction.